这是c++ builder的源码
//---------------------------------------------------------------------------
// Base64 code table
// 0-63 : A-Z(25) a-z(51), 0-9(61), +(62), /(63)
char __fastcall Base2Chr( Byte n )
{
n &= 0x3F;
if ( n < 26 )
return ( char )( n + 'A' );
else if ( n < 52 )
return ( char )( n - 26 + 'a' );
else if ( n < 62 )
return ( char )( n - 52 + '0' );
else if ( n == 62 )
return '+';
else
return '/';
}
//---------------------------------------------------------------------------
Byte Chr2Base( char c )
{
if ( c >= 'A' && c <= 'Z' )
return ( Byte )( c - 'A' );
else if ( c >= 'a' && c <= 'z' )
return ( Byte )( c - 'a' + 26 );
else if ( c >= '0' && c <= '9' )
return ( Byte )( c - '0' + 52 );
else if ( c == '+' )
return 62;
else
return 63;
}
AnsiString Base64Encode( AnsiString s )
{
int n = s.Length( );
Byte c, t;
AnsiString asTemp = "";
for ( int i = 1; i <= n; i++ )
{
c = s[i];
if ( i % 3 == 1 )
{
asTemp += Base2Chr( c >> 2 );
t = ( c << 4 ) & 0x3F;
}
else if ( i % 3 == 2 )
{
asTemp += Base2Chr( t | ( c >> 4 ) );
t = ( c << 2 ) & 0x3F;
}
else
{
asTemp += Base2Chr( t | ( c >> 6 ) );
asTemp += Base2Chr( c );
}
}
if ( n % 3 != 0 )
{
asTemp += Base2Chr( t );
if ( n % 3 == 1 )
asTemp += "==";
else
asTemp += "=";
}
return asTemp;
}
//---------------------------------------------------------------------------
//
AnsiString Base64Decode( AnsiString s )
{
int n = s.Length( );
Byte c, t;
AnsiString asTemp = "";
for ( int i = 1; i <= n; i++ )
{
if ( s[i] == '=' )
break;
c = Chr2Base( s[i] );
if ( i % 4 == 1 )
t = c << 2;
else if ( i % 4 == 2 )
{
asTemp += ( char )( t | ( c >> 4 ) );
t = ( Byte )( c << 4 );
}
else if ( i % 4 == 3 )
{
asTemp += ( char )( t | ( c >> 2 ) );
t = ( Byte )( c << 6 );
}
else
asTemp += ( char )( t | c );
}
return asTemp;
}